Engine surging and stalling, engine temp gauge fluctuating, where do I start?

I have a 2002 SL2 with 240k. I've noticed for the past couple of weeks that the gas milage was about 5 mpg below normal. The battery died on me last week, so I replaced it, but the alternator seemed to be fine as it was showing around 14.5v at 2000rpm and about 13.8v under full load (lights, radio, wipers, defrost, etc)

However, yesterday the engine starts surging and almost stalling, and the engine temp gauge was fluctuating. Quick test showed alternator at less than 13v with no load. So, I replaced the alternator last night. This morning it starts doing the same thing on my way to work. It's throwing two codes, P0118 (expected) and P0714( not expected). After searching the forums, likely suspects are the ETCS, CPS, or the PCM. But, which should I try first?

Re: Engine surging and stalling, engine temp gauge fluctuating, where do I start?

Thanks guys. After a few minutes rooting around, I found that one of the wires to the ECTS was bad. Luckily, I found a replacement connector locally, just have to wire it up tonight. Time to break out the soldering iron and heat shrink. I think I may also get some wire loom to better protect it.

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